nu·cle·o·syn·the·sis 
(n′klē-ō-sĭnthĭ-sĭs, ny′-)
(n′klē-ō-sĭnthĭ-sĭs, ny′-)n.
The process by which heavier chemical elements are synthesized from lighter atomic nuclei in the interiors of stars, during supernova explosions, and in the early stages of the universe.
nu′cle·o·syn·thetic (-sĭn-thĕtĭk) adj.